Studies on the clinical effectiveness of transfusions of granulocytes collected by Filtration Leukapheresis will be carried out in leukopenic and infected patients. The viability and functional adequacy of filtered granulocytes in-vitro and in-vivo will be evaluated. Improved methods for collection of granulocytes and monocytes by Filtration-Leukapheresis will be explored. The value of supportive granulocyte transfusions in enlarging the scope of currently available therapeutic modalities for malignant disorders will be determined.